1. Field of the Invention
This invention relates to a controller, and more particularly to a multi-range controller, such as a multi-range temperature controller, having a plurality of ranges with different scales and an input switch selectively connecting a preselected input signal and reference signals.
2. Description of the Prior Art
Referring to FIG. 1, a typical controller of the prior art has an amplifier 1 for amplifying an input signal, an analog-digital (to be referred to as A-D hereinafter) converter 2 for converting the thus amplified input signal into a digital signal, and a control unit 3 processing the digital signal so as to deliver a control signal at an output 4. The control unit 3 of the controller of the prior art has only one range of measurement or only one scale. Since different kinds of detectors with different scales are required for different applications, a wide variety of single-range controllers have been produced and used.
From the standpoint of manufacturers, the use of a wide variety of single-range controllers results in a disadvantage of non-availability of mass production, so that the production cost tends to be high and the delivery time tends to be long against the desire of end users for low cost and short delivery time.
On the other hand, from the standpoint of users, when a different range or scale becomes desirable due to change in operating conditions or the like, remodelling of the currently used controller or purchase of a new controller is necessary. Such remodelling and purchase result in a disadvantage of causing extra waiting time and extra expenditure.